Voltage-Gated Na+ Channels Enhance the Temporal Filtering Properties of Electrosensory Neurons in the Torus

• Published in: Journal of neurophysiology Vol. 90; no. 2; pp. 924 - 929
• Main Authors: Fortune, Eric S, Rose, Gary J
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.08.2003
• Subjects: Action Potentials - drug effects; Animals; Electrophysiology; Excitatory Postsynaptic Potentials - drug effects; Gymnotiformes; Lidocaine - analogs & derivatives; Lidocaine - pharmacology; Neurons, Afferent - drug effects; Neurons, Afferent - physiology; Sodium Channel Blockers - pharmacology; Sodium Channels - drug effects; Sodium Channels - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00294.2003

1 Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218 2 Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840 Submitted 26 March 2003; accepted in final form 9 May 2003 Regenerative processes enhance postsynaptic potential (PSP) amplitude and behaviorally relevant temporal filtering in more than one-third of electrosensory neurons in the torus semicircularis of Eigenmannia . Data from in vivo current-clamp intracellular recordings indicate that these "regenerative PSPs" can be divided in two groups based on their half-amplitude durations: constant duration (CD) and variable duration (VD) PSPs. CD PSPs have half-amplitude durations of between 20 and 60 ms that do not vary in relation to stimulus periodicity. In contrast, the half-amplitude durations of VD PSPs vary in relation to stimulus periodicity and range from approximately 10 to 500 ms. Injection of 0.1 nA sinusoidal current through the recording electrode demonstrated that CD PSPs and not VD PSPs can be elicited by voltage fluctuations alone. In addition, CD PSPs were blocked by intracellular application of either QX-314 or QX-222, whereas VD PSPs were not. These in vivo data suggest, therefore, that CD PSPs are mediated by voltage-dependent Na + conductances. Address for reprint requests: E. S. Fortune, Department of Psychological and Brain Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (E-mail: eric.fortune{at}jhu.edu ).